'Hurdle pretty high' to change taper: Fed's John Williams

Incremental changes in the nation's unemployment rate and economic outlook won't likely change the rate at which quantitative easing will be tapered, Federal Reserve Bank of San Francisco President John Williams said Wednesday.

"I think in my view, the hurdle is pretty high on changing the pace of the step-downs in our purchases that we started back in December," he said on CNBC's "Halftime Report. "

Williams emphasized taking a medium-term look at the data. "What I'm looking for is steady improvement in the labor market generally, and we are seeing that in other series that the government follows, such as job vacancies and perceptions of the job market," he said.

"I really don't want to overreact to any specific piece of data and really look at what it means for the medium-term trend."